1. Field of the Invention
This invention pertains to earth trenching equipment, and more particularly to apparatus for removing and installing trencher teeth.
2. Description of the Prior Art
Machines that cut trenches in the earth are subjected to severe operating conditions. That is especially true for the trencher teeth, which are carried in an endless track of chain links.
The trencher teeth are generally cylindrical in shape, having a head and a shank. The teeth are retained in respective collars in the chain links. The track is powered by the machine to move the teeth heads into direct sliding contact with soil, rocks, and water. That action imparts shock loads and abrasion to the teeth. For proper operation, it is important that the teeth rotate about their longitudinal axes as they are powered through the earth.
To increase the service lives of the teeth, their heads are usually hardened. In addition, it is well known to make the head working tips from a carbide material. Nevertheless, the teeth wear relatively rapidly, especially when used in rocky conditions. For economical operation of the trencher equipment, it is vital that a worn tooth be quickly replaced with a new tooth.
Prior trencher teeth were retained in the chain link collars by a band of thin resilient metal that fit loosely within a groove in the tooth shank. The band was cut through longitudinally, and the ends were spaced apart a short distance. Consequently, the band could collapse and expand radially. A number of small rounded bumps protruded from the band outer surface circumferentially around the band. The bumps of the uncollapsed band defined a circle having a diameter slightly larger than the diameter of the tooth shank. The prior trencher teeth were assembled to the chain link collars by inserting a tooth shank end into a close fitting hole in the collar until the band bumps contacted the collar. Then the tooth head was struck with a hammer or similar tool. The resulting impact on the tooth and the band bumps caused the band to radially collapse such that the bumps slid into the collar hole. The tooth was pushed into the collar until the band became aligned with a circumferential groove in the collar hole. At that point, the band resiliently returned to its original configuration, such that the bumps entered the collar groove. At that point, the tooth was firmly retained in the collar.
The prior tooth, band, and collar design was not entirely satisfactory. During operation, soil and small stones tended to become embedded in the tooth shank groove and in the collar groove. Consequently, the tooth seized in the collar and wore much faster than was tolerable.
A further disadvantage of the prior tooth design was that a worn tooth was difficult to remove. The design of the trenching machine chain links was such that the tooth could not be driven out from the shank end. The only way to remove the tooth was by using a forked puller tool. The fork was placed in a circumferential groove in the tooth head. A hard blow on the tool was required. That was because the pulling force had to be enough to collapse the band bumps from the collar groove. The tooth removal process was laborious and undesirably time consuming.
In an attempt to solve the problems associated with the band-type trencher teeth, a modified tooth with a longer shank was developed. The shank was long enough to extend completely through and emerge from the collar on the opposite side as the tooth head. A groove near the shank free end was exposed outside the collar. A heavy open keeper ring in the shank groove cooperated with the head to retain the tooth in the collar.
The new tooth design was an improvement. As one advantage, the tooth had a lesser tendency to seize in the collar.
However, installation and removal of the teeth remained difficult. The teeth shanks easily slid into the collar holes to expose the shank grooves, but the heavy and relatively rigid keeper rings were difficult to seat into and remove from the shank grooves. To seat a keeper ring, a mechanic was required to hold the keeper ring against the groove with one hand, usually using a pliers. He then struck the ring a hard blow, using a hammer, with his other hand. Ideally, the keeper ring would then instantaneously expand radially and slide fully into the groove. However, any misalignment of the keeper ring adjacent the tooth or inaccuracy of the hammer blow resulted in a failure to seat the keeper ring. In addition, the design of the trencher machine and track provided only limited space for the mechanic""s hands to hold the keeper ring and to swing the hammer.
It was even more difficult to remove the keeper ring from a worn tooth. The only practical way to remove the keeper ring was by manually prying its two ends apart with a pair of screwdrivers or the like. The mechanic was required to manipulate the screwdrivers together as levers acting against the keeper ring open ends. The screwdrivers had to simultaneously spread the keeper ring and apart and pry the keeper ring out of the shank groove. That process, performed in a limited space, was frustrating and time consuming. It was not unusual for a person to waste 15 minutes manually prying off the keeper ring from a single tooth.
Thus, a need exists for improvements in the way teeth are installed into and removed from trenching machines.
In accordance with the present invention, a slide hammer tool is provided that greatly eases the task of seating an open keeper ring onto and removing it from a cylinder. This is accomplished by apparatus that includes a heavy hammer handle that slides along a rod having opposite ends configured to conform to the shape of radial end surfaces of the keeper ring.
There are first and second stops near the respective ends of the rod that limit the travel of the hammer along the rod. The rod first end has two flat surfaces that are immoveable relative to each other and that lie in respective planes that converge toward a longitudinal centerline. There is a generally U-shaped cutout in the converging surfaces that is symmetrical about the longitudinal centerline. The cutout includes an arcuate surface that preferably is continuous and uninterrupted. The radius of the cutout arcuate surface is slightly larger than the radius of the cylinder. If desired, the cutout and the converging surfaces can be formed in a separate piece that is rigidly held to the first end of the rod.
The second end of the rod is configured with a concave surface having the same diameter as the keeper ring outer diameter. The depth of the concave surface is slightly less than the radial thickness of the keeper ring.
To remove a keeper ring from a cylinder using the slide hammer tool of the invention, the tool first end is used. The rod converging surfaces are placed in abutting contact against corresponding radial end surfaces of the keeper ring. The hammer is slid rapidly against the tool first stop. The impact on the first stop is transmitted to the two keeper ring radial end surfaces simultaneously. The tool converging surfaces act as a rigid wedge to expand the keeper ring end surfaces. The impact is sufficient to push the keeper ring off the cylinder.
To use the slide hammer tool to seat a keeper ring on a cylinder, the open end of the keeper ring is placed against the cylinder. The concave surface of the tool second end is placed in abutting contact against the keeper ring outer diameter opposite the keeper ring open end. The hammer is slid rapidly along the rod to strike the second stop. The impact of the hammer on the second stop is transmitted to the keeper ring, forcing its end surfaces to expand and slide over the cylinder and then immediately close. The keeper ring is then seated on the cylinder.
The method and apparatus of the invention, using rod ends that conform to the shape of a keeper ring, thus greatly simplifies the task of seating the keeper ring onto and removing it from a cylinder. The keeper ring is under spatial control at all times during the seating and removing processes, even though it is subjected to high impacts from the hammer.
Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention.